I think the implication is that in the shot, they needed Blade to open his eyes, but Wesley forgot to when it was shooting, and wasn't noticed until post-production, so they over-complicatedly filled in the using CGI

A lot of movies these days shoot in Canada (cheaper); from what I heard, Snipes was stoned almost EVERY DAY of that shoot, so it makes sense to think he was high. They had to use his body double for most shots, and CGI'd his face in except for CU's. Also, racists can shut the f*ck up, we're talking about one person here, not every blacktor.

Special effects laden movies can be very technical. Meryl streep apparently hated working on death becomes her, because she had to make movements and placements so perfectly, or act to a stick. Sometimes it's hard to act when you're so focused on getting the effects right. Wesley Snipes clearly cannot handle such complicated scenes where has to open his eyes.